The present invention relates to acrylic polymers which are formed by emulsion polymerization and as formed, are inherently tacky and functional as pressure-sensitive adhesives. More particularly, the adhesives of the instant invention have excellent guillotinability, room- and elevated-temperature adhesive performance and provide an ecologically safe replacement for solvent adhesives and other acrylic- and rubber-based emulsion adhesives.
Guillotinability is a critical requirement in film applications where pressure-sensitive adhesive (PSA) coated products are cut into sheet stock. During the process of guillotining it is expected that the adhesive will not build on the blades so that subsequent cutting is not affected and the cut sheets separate individually without sticking together. Solvent adhesives are commonly used in such applications due to the performance benefits they offer. Environmental constraints imposed on the use of solvents has caused the PSA industry to move away from solvent systems. The best alternative to day is the water borne adhesive technology due to adhesive user friendliness and the cost advantages. Obtaining high performance from water borne adhesive systems is the major task which the PSA industry is facing.
In terms of the instant invention U.S. Pat. Nos. 4,507,429, 4,694,056, and 4,725,639 to Lenney, and assigned to Air Products, Inc., pertain to a pressure-sensitive adhesive compositions and disclose increasing cohesive strength by use of polyfunctional monomers which include polyvinyl and polyallyl compounds including triallyl isocyanurate. Product glass transition temperature may be as high as -15.degree. C., limiting utility at reduced temperature.
We have sought to provide pressure-sensitive adhesives of improved properties which have broad utility including excellent guillotinability.